The present technology relates to a solid-state imaging device, a solid-state imaging device manufacturing method, and an electronic device employing this solid-state imaging device.
With solid-state imaging devices having a photoelectric conversion region, there is a solid-state imaging device having a configuration wherein multiple photoelectric conversion regions are disposed in the depth direction of a semiconductor substrate. With such a solid-state imaging device, a trench is formed in proximity to a photoelectric conversion region disposed in a depth position of the semiconductor substrate, and a readout gate is disposed within this trench via a gate insulating film.
With the solid-state imaging device thus configured, a channel is formed in a position along the gate insulating film between the depth position where the photoelectric conversion region is disposed and a floating diffusion within the semiconductor substrate. Signal charges accumulated in the photoelectric conversion region are read out to the floating diffusion via this channel by applying voltage to a readout gate embedded in the trench (see Japanese Unexamined Patent Application Publication No. 2009-295937).
Also, a configuration has been disclosed wherein a semiconductor substrate region where a channel between a photoelectric conversion region having an n-type impurity region disposed in a depth position of a semiconductor substrate and a floating diffusion made up of an n-type impurity region is formed is taken as an n-type impurity region having low concentration. With such a configuration, the photoelectric conversion region is completely depleted by adjusting the n-type impurity concentration, whereby all of the signal charges can be transferred (see Japanese Unexamined Patent Application Publication No. 2010-114322).
Also, with regard to rear face irradiation type solid-state imaging devices, improvement in saturation charge amount, and high sensitivity have been demanded.
As a configuration for increasing saturation charge amount, a solid-state imaging device has been proposed wherein multiple photodiodes are formed in the depth direction within a substrate (see Japanese Unexamined Patent Application Publication No. 2010-114274). With this configuration, saturation charge amount is increased by laminating three photodiodes (PD1, PD2, and PD3) formed with PN junction between an n-type semiconductor region and a p-type semiconductor region on the n-type semiconductor region in the depth direction. Additionally, a vertical-type gate electrode embedded in the depth direction from the surface of the substrate is provided as a transfer transistor (Tr). Electric charges are transferred to the floating diffusion (FD) from a photodiode PD formed in a depth position of the substrate using this vertical-type Tr.
Also, as for a configuration for enabling high sensitivity, a solid-state imaging device has been proposed wherein a second photodiode PD2 is provided on the light incident side (substrate rear face), and a first photodiode PD1 is provided on the opposite face (substrate front face) on the light incident side (see Japanese Unexamined Patent Application Publication No. 2010-192483).
With this solid-state imaging device, the first photodiode PD1 and floating diffusion (FD) and so forth are formed by injecting ions into the surface of the semiconductor substrate. Further, after forming a gate electrode, a wiring layer, or the like on the semiconductor substrate, the semiconductor substrate is reversed, and the rear face of the semiconductor substrate is ground.
Next, ions are injected from the rear face side of the semiconductor substrate to perform activation of impurities by heat treatment of 1000° C. such as laser annealing or the like for example to form a second photodiode PD2 and so forth.